Anesthetics are substances used to induce a loss of sensation or consciousness, primarily during medical procedures to prevent pain. They can be classified into two main categories: local anesthetics, which numb a specific area of the body, and general anesthetics, which induce a complete loss of awareness and sensation throughout the body. Anesthetics work by interfering with nerve signals in the brain and body. They are essential in surgeries and various medical interventions to ensure patient comfort and safety.